TE.sub.011 filters have traditionally been quite difficult to work with because the structures used did not have removable irises. Mistakes required scrapping the entire housing.
A typical prior art TE.sub.011 filter is the ladder type which has been described by Mattaei in a book entitled "Microwave Filters, Impedance Matching Networks, and Coupling Structures," McGraw Hill, N.Y., 1964, pages 921-937. Another prior art contribution to this field is a side-coupled structure which achieved a subset of the canonical bridge couplings, and has been described by Atia and Williams in an article entitled "General TE.sub.0111 Mode Bandpass Filters," IEEE MIT-24, October 1976.